Prevalence and risk factors for allergic sensitization: 3 cross-sectional studies among schoolchildren from 1996 to 2017

Abstract

Background: The prevalence of allergic sensitization and allergic diseases has increased for decades in Northern Europe, but recent studies are lacking.

Objective: We sought to study the prevalence trends of allergic sensitization, associated risk factors, and the association with asthma and allergic rhinitis (AR) among children in Northern Sweden.

Methods: Three cohorts of children aged 7 to 8 years participated in a skin prick test (SPT) with 10 airborne allergens in 1996, 2006, and 2017, with 2148, 1693, and 1762 participants tested, respectively, representing 87% to 90% of schoolchildren in the catchment communities. Adjusted Poisson regression was used to identify risk factors for allergic sensitization and the association with asthma and AR.

Results: The prevalence of any positive SPT response increased from 21% in 1996 to 30% in 2006 and remained at 30% in 2017 (P < .001). Sensitization to cat was the most common for all the years. The risk factor pattern for a positive SPT response was similar in all examinations, with positive and significant associations with a family history of allergy (risk ratio, 1.4-1.5) and negative and significant associations with having a cat at home (risk ratio, 0.7-0.8). The prevalence of physician-diagnosed asthma increased, but the association with allergic sensitization weakened. The opposite trends were found for AR-decreasing prevalence and strengthened association with allergic sensitization.

Conclusions: The prevalence of allergic sensitization increased from 1996 to 2006 but plateaued in the next decade, whereas the risk factor pattern remained stable. The diverging trends of associations between allergic sensitization and asthma and AR suggest secular trends in the clinical management of allergic diseases.

Keywords: Allergic sensitization; OLIN; allergic rhinitis; asthma; epidemiology; schoolchildren; skin prick test.

Fig 1

Prevalence (%) of allergic sensitization to airborne allergens defined by SPT among 8-year-old children by study year. Difference in proportions was analyzed using the χ² test.

Fig 2

Risk for allergic sensitization in relation to number of exposures suggestive of higher microbiome diversity (ever having a dog at home, ever having a cat at home, rural living first year of life, and ever living on a farm) in a pooled analysis of all 3 cohorts. Analyzed by Poisson regression and adjusted for sex, family history of allergic disease, number of siblings, type of living first year of life, and study year, expressed as RR with 95% CI.

Fig 3

The association between allergic sensitization and current asthma and AR, respectively, by study year. Analyzed by Poisson regression and adjusted for sex, family history of asthma or AR, respectively, maternal smoking in pregnancy, severe respiratory infection, breast-feeding for less than 3 months, and ever having a cat at home, expressed as RR with 95% CI.